“Why is it important to hold back information about Russians and it’s not important to hold back information about a Democratic candidate for president? It is mind-boggling, and Director [James] Comey needs to answer this,” Clinton campaign manager Robby Mook said on CNN’s “New Day.”

“We just want fairness,” he said. “He thought it was perfectly fine for the FBI to send a letter to Capitol Hill about information they had never looked at and say, ‘Hey, we have some information, Republican chairmen — do you want to speculate on what it might be?’ “

“He knew they would leak that letter. He knew that there would be false headlines,” Mr. Mook said. “The reporting was breathless on Friday. A lot of what was reported had to be rolled back because it was mischaracterized by Republicans.”

Mr. Comey informed Congress on Friday that, through an unrelated case, the bureau had learned about the existence of emails that appear to be relevant to the investigation into Mrs. Clinton’s private email set-up.

“If Director Comey was so concerned about how information would be handled and about the reputation of the FBI, why did he release this letter that was full of innuendo and absolutely no facts? It is mind-boggling,” Mr. Mook said.

Mr. Mook said information on Mr. Trump and his potential ties to Russia should also be out there now.

“Now that he has opened the door, now that he has weighed into this election, we’re saying let’s get all the information out there,” he said.

“Let’s get the information out on Hillary Clinton that he supposedly might have,” he said. “Let’s get the information out on Donald Trump. The voters are smart, and they can figure this out.”